The present invention relates to a novel process to form 2-amino-1,3-propanediol (commonly known as "serinol"). The present process provides a means of forming serinol using readily formed materials under mild and easily handled conditions suitable for industrial application.
Serinol is a highly desired material required for the preparation of nonionic x-ray contrast media, such as iopanediol (N,N'-bis[2-hydroxy-1-(hydroxymethyl)ethyl]-2,4,6-triiodo-5-lactamidisopht halamide).
Serinol has been previously prepared from 2-oximino-1,3-propanediol, 2-nitro-1,3-propanediol, serine, serine methyl ester, or oximinomalonic acid diethyl ester. In most cases the required processes provided low yields and, in certain instances, utilizes poorly accessible starting materials. In addition, the processes normally entail the generation of decomposable and dangerous imtermediates which require special equipment and handling practices. The expense of the reactants and equipment required, as well as the special handling needed leads to unsatisfactory processes for industrial application.
The major commercial method of producing serinol is disclosed in U.S. Pat. No. 4,448,999 and involves an improvement of a process disclosed in DE No. 2,742,981. The process requires the initial formation of a solid product, sodium nitro-1,3-propanediol. The diol must be removed from the reaction zone in order to minimize unwanted further reaction to the triol. The diol is then subjected to hydrogenation at elevated pressures of 50 bars or greater in the presence of palladium on carbon as the hydrogenation catalyst. U.S. Pat. No. '999 discloses that the hydrogenation process should be carried out under stringent temperature conditions to achieve consistently good yields. The difficulty with this method is the need for isolating and utilizing sodium nitro-1,3-propanediol which is known to be an unstable material which decomposes with catastrophic results.
An alternate method for producing serinol is disclosed in DE No. 2,829,916. This process involves the reductive amination of 1,3-dihydroxyacetone. Due to the difficulty in synthesizing the required starting ketone, this process is not economically competitive and is not widely used on an industrial scale.
It is highly desired to have a process capable of forming serinol which utilizes readily available and easily handled materials.